1. Field of Invention
This invention relates to a distributed method and apparatus that allocates a communication medium via efficient arbitration techniques.
2. Description of Related Art
Conventionally, management of a communication medium requires either a centralized head-end to control arbitration among end-users (e.g., telephone stations or personal computers, for example) or end-users randomly competing for access. While centrally controlled arbitration may provide guaranteed access, an end-user must first arbitrate successfully before transmitting end-user information. This management scheme undesirably requires an arbitration overhead time to be added to a data transmission time as well as centralized arbitration hardware to manage the arbitration.
On the other hand, while overhead is avoided by random competition techniques such as Ethernet protocol, end-users are not guaranteed access. Thus, new technology is required to reduce overhead and guarantee access to communication mediums.
The invention provides a method and apparatus for end-users to allocate a communication medium locally without requiring a central arbitration device. The end-users are coupled together via a first upstream signaling channel, a first downstream signaling channel, a second upstream signaling channel, a second downstream signaling channel, a downstream data channel and an upstream data channel. The end-users bid for control of the upstream data channel by arbitrating on the first and second upstream signaling channels. When an end-user desires to gain control of the upstream data channel, both auction data and address data are transmitted concurrently on the first and second upstream signaling channels, respectively. When data received by the end-user from the first and second downstream signaling channels matches the auction and address data, the end-user wins the bid and gains control of the upstream data channel. However, if the data received from the first downstream signaling channels does not match the auction data, the end-user backs off from the first and second upstream signaling channels and refrains from bidding for control of the upstream data channel until the first and second upstream signaling channels become quiet. In all other cases the end-user will continue to bid.
The auction data values may be used to set priorities among the end-users. During a first few auction cycles, each of the end-users transmit auction data values according to a priority preassigned by a head-end, for example. After the first few auction cycles, only the highest priority end-users remain to bid for control of the upstream data channel. For subsequent auction cycles, the remaining end-users generate auction data values randomly to bid for control of the upstream data channel.
The auction data values and the address bits are transmitted concurrently when each of the end-user is bids for control of the upstream data channel. Concurrent transmission of the auction data values and address bits increases the efficiency of the communication medium allocation process. In addition, the end-users may also transmit data on the upstream data channel while transmitting the auction data values and address bits. For this case, the time required to transmit both the auction data values and address bits are overlapped by the data transmission so that if only one user arbitrates for control of the upstream data channel, no overhead is expended for the arbitration process. If data is transmitted on the,: upstream data channel in frames, bidding for control of the upstream data channel may be performed while another end-user is transmitting data on the upstream data channel. Thus, the time required for gaining control of the upstream data channel is completely masked by the data transmission time.